a) Field of the Invention
The present invention relates to a method of manufacturing a field emission device, and more particularly to a method of manufacturing a field emission device having an emitter tip with a small radius of curvature and a small apex angle.
b) Description of the Related Art
A field emission element emits electrons from a sharp tip of an emitter (electric field emission emitter) by utilizing electric field concentration. For example, a flat panel display can be structured by using a field emitter array (FEA) having a number of emitters. Each emitter controls the luminance or the like of a corresponding pixel of the display.
A conventional manufacture method of a field emission device will be described. First, an emitter having a starting rough shape is made of emitter material. Thereafter, a focussed ion beam (FIB) is applied to the tip of the emitter to make a sharp emitter tip. This technique is disclosed In "Tip Surface Modification of Si Field Emitter Arrays" by M. Takai et al, Proceedings of the 2nd International Display Workshops, Oct. 19, 1995 at Hamamatsu City, Shizuoka, Japan.
This technique makes the emitter sharp by using FIB. Specifically, ions of material having a large atomic weight, such as Ga, are converged into a beam having a very small diameter by using an electronic lens or the like, and this beam is applied to an emitter.
The diameter of the beam is 20 to 240 nm which is smaller than the tip diameter of an emitter. In order to apply the beam to each emitter for a predetermined time, high precision alignment is required. With a manufacture method using FIB, the process time becomes long as the-number of emitters becomes large.
With the method using FIB, a lens system for passing a beam therethrough is required in order to form an effective beam, and also an alignment system is required to precisely align the tip of each emitter with the beam, because the beam diameter is small. Since the lens and alignment systems are required, the manufacture system becomes complicated and expensive.
With this method, since a beam is applied to each emitter after alignment, it takes a long time to sharpen the tips of all emitters. Furthermore, since the lens and alignment systems are required, the manufacture system becomes complicated and expensive.